Backlash prevention system and method

ABSTRACT

An optical module includes a first optics group, a second optics group, and an image sensor, wherein the first optics group and second optics group are configured to provide an image having a focus and a magnification to the image sensor. In some embodiments of the present invention, a first optics assembly includes a first optics group coupled to a threaded portion of a first lead screw so that rotation of the first lead screw results in translation of the first optics group along an axis of the first lead screw, a first actuator for rotating the first lead screw; and a first sensing target configured to permit detection of rotation of the first lead screw. In some embodiments of the present invention a second optics assembly includes a second optics group coupled to a threaded portion of a second lead screw so that rotation of the second lead screw results in translation of the second optics group along an axis of the second lead screw, a second actuator for rotating the second lead screw, and second means for sensing configured to detect rotation of the second lead screw.

RELATED APPLICATIONS

This Patent Application is a Divisional Application which claimspriority under 35 U.S.C. 121 of the co-pending U.S. patent applicationSer. No. 11/514,811, filed Sep. 1, 2006, now U.S. Pat. No. 7,531,773entitled “AUTO-FOCUS AND ZOOM MODULE” which claims priority under 35U.S.C. 119(e) of U.S. Provisional Pat. App. No. 60/715,533, filed Sep.8, 2005, entitled “3× ZOOM MINI MODULE”, both of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The disclosure relates to camera optics, specifically an auto-focus andzoom module.

BACKGROUND

Recently, there have been numerous developments in digital cameratechnology. One such development is the further miniaturization ofoptical and mechanical parts to the millimeter and sub millimeterdimensions. The shrinkage in the moving parts of cameras has allowed theimplementation of modern digital camera and optical technology into abroader range of devices. These devices are also constantly beingdesigned and constructed into smaller and smaller form factorembodiments. For example, commercially available personal electronicdevices such as cellular phones, personal digital assistants (PDAs), andwrist and/or pocket watches include a miniature digital camera.Moreover, larger form factor devices are also packed with additionalfeatures. For example, a typical video camcorder often has an entiredigital camera for “still” photography built into the camcorder devicealong with the mechanisms and circuitry for motion video recording.

Typically, however, modern digital camera implementations suffer from avariety of constraints. Some of these constraints include cost, size,features, and complexity. For instance, with a reduction in sizetypically comes an increase in cost, a reduction in features and/or anincrease in complexity.

SUMMARY OF THE DISCLOSURE

The present invention is for an optical module. The optical module has afirst optics group, a second optics group, and an image sensor. Thefirst optics group and second optics group are configured to provide animage having a focus and a magnification to the image sensor.

In some embodiments of the present invention, an optics module includesa first optics group coupled to a threaded portion of a first leadscrew. Rotation of the first lead screw results in translation of thefirst optics group along an axis of the first lead screw. A firstactuator rotates the first lead screw. A first sensing target isconfigured to permit detection of rotation of the first lead screw. Insome embodiments of the present invention the optical module furthercomprises a second optics group coupled to a threaded portion of asecond lead screw. Rotation of the second lead screw results intranslation of the second optics group along an axis of the second leadscrew. A second actuator rotates the second lead screw. A second meansfor sensing is configured to detect rotation of the second lead screw.

A housing can be included as well. The first optics assembly, secondoptics assembly, and, are mounted within the housing.

The first sensing target can include a closed surface having adjacentregions of differing optical properties arranged in an alternatingpattern symmetric about the axis or rotation of the first lead screw.The second sensing target can include a closed surface having adjacentregions of differing optical properties arranged in an alternatingpattern symmetric about the axis or rotation of the second lead screw.Preferably, the second sensing target is configured to permitmeasurement of translation of the second optics group along the secondlead screw. The first sensing target is configured to permit measurementof translation of the first optics group along the first lead screw.Most preferably, the first sensing target permits measurement over arange of at least 10 mm with a resolution of less than 10 microns. Thesecond sensing target permits measurement over a range of at least 2 mmwith a resolution of less than 10 microns.

In some embodiments, the first lead screw includes a threaded portionhaving a first outer thread diameter, a non-threaded portion having afirst outer diameter, and a first actuator registering feature. Thefirst optics group is coupled to the threaded portion of a first leadscrew so that rotation of the first lead screw results in translation ofthe first optics group along an axis of the first lead screw. A firstgearlash prevention spring is configured to bias the first optics grouptoward the non-threaded portion of the first lead screw. A firstcylindrical vibrational actuator rotates the first lead screw. The firstcylindrical vibration actuator is held over the non-threaded portion andagainst the actuator registering feature of the first lead screw by aspring force from a first preload spring that abuts both the housing andthe first actuator. The first cylindrical vibrational actuator isconstrained at a node point by a flexible coupling to the housing. Firstmeans for sensing detects rotation of the first lead screw.

In some embodiments, the first outer thread diameter is greater than thefirst outer diameter. In other embodiments the first outer threaddiameter is less than the first outer diameter. In yet otherembodiments, the first outer thread diameter and the first outerdiameter are equal.

In some embodiments the second lead screw a second lead screw includes athreaded portion having a second outer thread diameter, a non-threadedportion having a second outer diameter, and a second actuatorregistering feature. The second optics group is coupled to the threadedportion of a second lead screw so that rotation of the second lead screwresults in translation of the second optics group along an axis of thesecond lead screw. A second gearlash prevention spring is configured tobias the second optics group toward the non-threaded portion of thesecond lead screw. A second cylindrical vibrational actuator rotates thesecond lead screw. The second cylindrical vibrational actuator is heldover the non-threaded portion and against the actuator registeringfeature of the second lead screw by a second preload spring that abutsboth the housing and the second actuator. The second cylindricalvibrational actuator is constrained at a node point by a flexiblecoupling to the housing. Second means for sensing detects rotation ofthe second lead screw.

Preferably, the first actuator registering feature is disposed betweenthe threaded portion and the non-threaded portion of the first leadscrew. Also preferably, the second actuator registering feature isdisposed between the threaded portion and the non-threaded portion ofthe second lead screw.

In some embodiments, the second outer thread diameter is greater thanthe second outer diameter. In other embodiments, the second outer threaddiameter is less than the second outer diameter. In yet otherembodiments, the second outer thread diameter and the second outerdiameter are equal.

Some embodiments of the present invention relate to an auto focus andzoom module that includes a cylindrical vibrational actuator of the typethat oscillates in a standing wave pattern to drive a shaft placedtherein to rotate. An auto focus and zoom module in accordance withthese embodiments comprises a housing, an optics assembly, and an imagesensor, wherein the optics group is configured to provide an imagehaving a focus and a magnification to the image sensor. The opticsassembly comprises a lead screw including a threaded portion having anouter thread diameter, a non-threaded portion having an outer diameter,and an actuator registering feature. An optics group is coupled to athreaded portion of the lead screw so that rotation of the lead screwresults in translation of the optics group along an axis of the leadscrew. A cylindrical vibrational actuator rotates the lead screw heldover the non-threaded portion and against the actuator registeringfeature of the lead screw by a preload spring that abuts both thehousing and the actuator and constrained at a node point of itspreferred standing wave pattern by a flexible coupling to the housing.Means for sensing detects rotation of the lead screw. Preferably, theactuator registering feature is disposed between the threaded portionand the non-threaded portion

In some embodiments of the present invention, an auto-focus and zoommodule comprises a first guide pin, a second guide pin, a first opticsassembly, a second optics assembly, and an image sensor, wherein thefirst optics group and second optics group are configured to provide animage having a focus and a magnification to the image sensor.

In some embodiments, a first optics assembly includes a first lead screwincluding a threaded portion having a first outer thread diameter, anon-threaded portion having a first outer diameter, and an actuatorregistering feature wherein the actuator registering feature is disposedbetween the threaded portion and the non-threaded portion. A firstoptics group includes a first spring-hinged assembly of two threadedcoupling arms arranged in opposition and configured to couple with thethreaded portion of the first lead screw. Thus, rotation of the firstlead screw results in translation of the first optics group along anaxis of the first lead screw. The spring hinge assembly is coupled toand coupled to the first guide pin and the second guide pin. A firstactuator rotates the first lead screw. First means for sensing to detectrotation of the first lead screw.

In some embodiments the first outer thread diameter is greater than thefirst outer diameter. In other embodiments, the first outer threaddiameter is less than the first outer diameter. In yet otherembodiments, the first outer thread diameter and the first outerdiameter are equal.

Some embodiments of the present invention relate to a method ofpreventing backlash in a system using a threaded lead screw as a driveelement. The method comprises the steps of providing a lead screw havingan axis and a threaded region with a thread depth and thread pitch. Aspring-hinged assembly of a plurality of teethed coupling arms isarranged in opposition and configured to couple with the threadedportion of the lead screw rotation of the lead screw results intranslation of the second optics group along an axis of the second leadscrew. wherein teeth of the teethed coupling arms have a tooth depth andtooth pitch, wherein the tooth depth is substantially less than thethread depth, and the tooth pitch is greater than the thread pitch.

In accordance with the present invention an optical module preferablyincludes a prism element coupled to an optics group, wherein the prismdirects to the optics group an image that is at an angle with respect toa plane of the module.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth in the appendedclaims. However, for purpose of explanation, several embodiments of theinvention are set forth in the following figures.

FIG. 1 is a perspective view of an auto-focus and zoom module inaccordance with some embodiments of the invention.

FIG. 2 is a perspective view of an auto-focus and zoom module inaccordance with some embodiments of the invention.

FIG. 3 is a side view of a lead screw assembly of an auto-focus and zoommodule in accordance with some embodiments of the invention.

FIG. 4 is a sectional plan view of an auto-focus and zoom module inaccordance with some embodiments of the invention.

FIG. 5A is a sectional perspective view of an auto-focus and zoom modulein accordance with some embodiments of the invention.

FIG. 5B is a sectional perspective view of an auto-focus and zoom modulein accordance with some embodiments of the invention.

FIG. 5C is a sectional perspective view of an auto-focus and zoom modulein accordance with some embodiments of the invention.

FIG. 6 is a side view of an auto-focus and zoom module in accordancewith some embodiments of the invention.

FIG. 7A is a sectional schematic representation of a coupling mechanismemployed in an auto-focus and zoom module in accordance with someembodiments of the invention.

FIG. 7B illustrates a coupling using threads of different pitch inaccordance with some embodiments of the invention.

FIG. 8A is a schematic representation of a distance sensor in accordancewith some embodiments of the invention.

FIG. 8B is a schematic representation of beam spreading that occursduring distance sensing in accordance with some embodiments of theinvention.

FIG. 8C is a schematic representation of beam spreading that occursduring distance sensing in accordance with some embodiments of theinvention.

FIG. 9A is a schematic illustration of a direct imaging solution fordistance sensing in schematic representation of beam spreading thatoccurs during distance sensing in accordance with some embodiments ofthe invention.

FIG. 9B is a schematic illustration of a lens-based imaging solution fordistance sensing in accordance with some embodiments of the invention.

FIG. 9C is a schematic illustration of a pinhole-based imaging solutionfor distance sensing in accordance with some embodiments of theinvention.

FIG. 10 is an exploded perspective view of an assembly for positionsensing in accordance with some embodiments of the invention.

FIG. 11 is an exploded perspective view of an assembly for positionsensing in accordance with some embodiments of the invention.

FIG. 12A is a sectional view of a portion of an assembly illustrating anactuator mount consistent with some embodiments of the presentinvention.

FIG. 12B is a sectional view of a portion of an assembly illustrating anactuator mount consistent with some embodiments of the presentinvention.

FIG. 12C is a sectional view of a portion of an assembly illustrating anactuator mount consistent with some embodiments of the presentinvention.

FIG. 12D is a sectional view of a portion of an assembly illustrating anactuator mount consistent with some embodiments of the presentinvention.

DETAILED DESCRIPTION

In the following description, numerous details and alternatives are setforth for the purpose of explanation. However, one of ordinary skill inthe art will realize that the invention can be practiced without the useof these specific details. In other instances, well-known structures anddevices are shown in block diagram form in order not to obscure thedescription of the invention with unnecessary detail.

A. Structural

FIG. 1 illustrates an auto-focus and zoom module 1000 in accordance withsome embodiments of the invention. As shown in this figure, the module1000 includes a front optics group 400, a rear optics group 500, and animage sensor 1010. The front optics group 400 and rear optics group 500typically comprise one or more optical elements such as a lens. Forinstance, the module 1000 illustrated in FIG. 4 includes several opticallenses in both the front optics group 400 and rear optics group 500.However, one of ordinary skill will recognize both more complex andsimpler arrangements for the optics groups.

B. Assembly Details

FIGS. 1 and 2 illustrate further details of module 1000. The module ofsome embodiments comprises a front and rear housing coupled to oneanother and aligned by guide pins. The guide pins are further used toguide movement of the barrels. FIG. 5A illustrates the housing,comprising the rear component 1050 and the front component 1060, whichprovides a structural frame for the various assemblies of the module1000. The lead screw assemblies 200 and 300, as well as the guide pins600 and 700 are coupled to the housing. This coupling positions andsecures the components relative to one another, and to the target region1012 of the image sensor 1010, providing a chassis for an auto-focus andzoom module capable of providing an image with a magnification and zoomto the target region 1012.

Attached to the front housing are the front barrel and optionally aprism. The housing of the module preferably further includes a casingand a cover mechanism. The cover mechanism preferably prevents lightleakage and dust contamination from affecting the internal components ofthe module, particularly the lens groups and the image sensor. Attachedto the rear housing are the image sensor and, optionally, an infrared(IR) filter and/or a low pass filter.

Image Sensor

As shown in the figures, the image sensor 1010 defines preferably aplane. In FIG. 1, this plane is parallel to an x-y plane. Typically, themodule 1000 is configured to provide an image to the image sensor 1010along an image vector parallel to a z-axis.

Guide Pins

FIG. 1 illustrates a guide pin arrangement for an auto-focus and zoommodule in accordance with some embodiments. Some embodiments include apair of guide pins, while some embodiments employ a different number ofguide pins. Regardless of their number, the guide pins 600 and 700 aretypically mounted along a linear axis of the module 1000 to permit therear barrel 530 and the front barrel 430 to move relative to the imagesensor 1010. In the module 1000, the primary guide pin 600 and thesecondary guide pin 700 are aligned so that their axes are substantiallyparallel to each other and to the z-axis. Further, the lead screwassemblies 200 and 300 are also aligned so that their axes aresubstantially parallel to each other, the z-axis, and the guide pins 600and 700.

Typically, the guide pins 600 and 700 are coupled to the front component1050 and the rear component 1060 of the housing on opposite sides of theimage vector of the image sensor 1010. However, one skilled in the artwill recognize that other configurations are possible. The lead screws200 and 300 are typically coupled to the front component 1050 and therear component 1060 of the housing on the same side of the image sensor1010.

In some embodiments, the range of motion provided to the rear barrel 530by the guide pins 600 and 700 is approximately 7 millimeters. In someembodiments, the range of motion provided to the front barrel 430 theguide pins 600 and 700 is approximately 2 millimeters. Due to this rangeof motion, however, the guide pins 600 and 700 of some embodiments oftenaffect the form factor of the module 1000. Hence, some embodimentsfurther include means for modifying and/or concealing the form factor ofthe module 1000.

Prism Feature

An optional prism feature can also be included. This feature allows theauto-focus and zoom module to be disposed and/or mounted in a variety oforientations. For instance, the horizontal width of a particularimplementation is often limited such that the module is preferablydisposed lengthwise in the vertical plane of an enclosure. Thisorientation allows the range of motion of the front and rear barrelsalong the guide pins, as described above, to be implemented in a devicehaving a small width and/or depth form factor.

FIGS. 1 and 5B illustrate a prism feature of some of these embodiments.FIG. 1 includes a module 1000 with a prism 100 mounted at the frontbarrel 430. The prism 100 redirects the light from an image at an anglewith respect to the front barrel 430. As described above, the frontbarrel 430 typically houses a front lens group. The front lens groupcontains one or more front optical elements such as the front lens 440illustrated in FIG. 5B. Hence the prism 100 allows the module 1000 to bedisposed in a variety of orientations within a device that is typicallyheld at an angle with respect to the subject being viewed and/orphotographed.

FIG. 5B illustrates the small form factor of a prism 100 mounted on amodule 1000 in accordance with some embodiments. In these embodiments,the combination of a prism holder and a prism bracket advantageouslymount the prism adjacent to the front lens 440 of the module 1000. Asdescribed above, the prism 100 typically redirects light from a subjectimage that is at an angle with respect to the front lens 440 of themodule 1000.

Lens System

As shown in the figures, the rear optics group 500 and front opticsgroup 400 have a predefined constructions. The rear optics group 500further includes the rear barrel 530, the rear guide sleeve 510, and therear guide slot 520. The rear barrel typically houses one or more lensesor other optical elements. As illustrated, the rear barrel 530 housesthe rear lens 540. The rear barrel 530 is a substantially cylindricalbody with a central axis. The rear lens 540 is configured to directlight along the central axis of the rear barrel 530. The rear guidesleeve 510 is an elongated, substantially cylindrical body coupled tothe rear barrel 530 so that the central axis of the rear barrel 530 andan axis of the rear guild sleeve 510 are substantially parallel. Therear guide slot 520 is a slotted feature configured to interface with acylinder.

The front optics group 400 further includes the front barrel 430, thefront guide sleeve 410, and the front guide slot 420. The front barreltypically houses the front lens 440 (e.g. of FIG. 5B). The front barrel430 is a substantially cylindrical body with a central axis. The frontlens 440 is configured to direct light along the central axis of thefront barrel 430. The front guide sleeve 410 is an elongated,substantially cylindrical body coupled to the front barrel 430 so thatthe central axis of the front barrel 430 and an axis of the front guildsleeve 410 are substantially parallel. The front guide slot 420 is aslotted feature configured to interface with a cylinder.

Lens-Guide Pin Interface

Referring now to FIG. 5B, the front optics group 400 includes the frontguide sleeve 410, which couples with the primary guide pin 600. Asillustrated, the front guide sleeve 410 is substantially elongatedrelative to the front barrel 430. Further, the front guide sleeve 410 isrigidly connected to the front barrel 430. This configuration preventsthe front optics group 400 from rotating within the y-z plane or x-zplane relative to the primary guide pin 600, but permits rotation withinthe x-y plane, assuming the guide pin 600 lies along the z-axis. Therear optics group 500 includes the rear guide sleeve 510, which coupleswith the primary guide pin 600. As illustrated, the rear guide sleeve510 is substantially elongated relative to the rear barrel 530. Further,the rear guide sleeve 510 is rigidly connected to the rear barrel 530.This configuration prevents the rear optics group 500 from rotatingwithin the y-z plane or x-z plane relative to the primary guide pin 600,but permits rotation within the x-y plane, assuming the guide pin 600lies along the z-axis.

Referring now to FIG. 1, the front optics group 400 also includes thefront guide slot 420, configured to couple with the secondary guide pin700. The coupling between the guide slot 420 and the secondary guide pin700 prevents the front optics group 400 from rotating within the x-yplane relative to either of the guide pins 600 and 700. The couplingbetween the front optics group 400 and guide pins 600 and 700 permitsthe front optics group 400 to translate along the axis defined by thetwo guide pins (the z-axis in FIG. 1), but not to move in either of theaxes orthogonal to that axis (here the x and y axes).

The rear optics group 500 also includes the rear guide slot 520,configured to couple with the secondary guide pin 700. The couplingbetween the guide slot 520 and the secondary guide pin 700 prevents therear optics group 500 from rotating within the x-y plane relative toeither of the guide pins 600 and 700. The coupling between the rearoptics group 500 and guide pins 600 and 700 permits the rear opticsgroup 500 to translate along the axis defined by the two guide pins (thez-axis in FIG. 1), but not to move in either of the axes orthogonal tothat axis (here the x and y axes).

Lead Screw Assemblies

Referring now to FIG. 3, the exemplary lead screw assembly 300′ is showncoupled with the sectioned housing comprising the rear component 1050′and the front component 1060′. The lead screw assembly 300′ isstructured around the lead screw 1. The assembly includes the actuator20, the coupling nut 35, and the sensing target 50. In addition, theassembly includes the preload spring 10 and the anti-gearlash spring 40.The lead screw 1 comprises a threaded region 5 and two non-threadedregions. The actuator 20 is coupled with a first non-threaded region,while the sensing target 50 is coupled with a second non-threadedregion. When coupled to the housing, the lead screw assembly 300′contacts specialized features of the rear component 1050 and the frontcomponent 1060′. These features include the lead screw retention wells1051 and 1065, and the gearlash spring reference feature 1063.Preferably, these features comprise bearings configured to facilitaterotation of the lead screws.

FIG. 5C illustrates a lead screw assembly 300, of the type shown in FIG.3, coupled with a sectioned housing comprising the front component 1060and the rear component 1050. As illustrated, the axis of the lead screw300 is parallel with optical path formed through the lens groups of therear optics group 500 and the front optics group 400.

Sensing Target

A lead screw assembly in accordance with some embodiments of the presentinvention includes a sensing target. The lead screw assembly 300′ ofFIG. 3 includes a sensing target 50 disposed between the lead screwretention well 1063 and the gearlash spring reference feature 1063.Typically, a sensing target includes a feature that interfaces with aregistering feature of the second non-threaded region of a lead screw.For example, as can be seen in the partial cross-sectional viewillustrated in FIG. 5A, the lead screw 260 includes registering featureswithin its non-threaded regions. As shown, the second non-threadedregion of the lead screw 260 includes the sensor target-registeringfeature 261. The registering feature 261 is configured to interface withcorresponding features of the sensing target 250.

Actuator

The actuator 20 is positioned over a portion of the first non-threadedregion. Typically, the actuator 20 includes a feature that interfaceswith a registering feature of the first non-threaded region of the leadscrew 1. For example, as shown in FIG. 5A, the lead screw 260 includesthe actuator-registering feature 263 within its first non-threadedregion. The actuator-registering feature 263 and corresponding featuresof the actuator 220 are configured to interface with one another.

Further, the actuator 20 is typically coupled to the housing throughmultiple means. In the lead screw assembly 300′, the preload spring 10couples the actuator 20 to the rear component 1050 of the housing,urging the actuator 20 against a referencing feature of the lead screw1. In another example, the lead screw assembly 200 of FIG. 5A includesthe preload spring 210 that exerts spring forces on both the rearcomponent 1050 of the housing and on the actuator 220, to force afeature of the actuator 220 against the actuator-registering feature 263of the lead screw 260. Other arrangements of actuator, preload spring,and registering feature(s) are discussed below with reference to FIGS.12A-12D.

Another coupling means are actuator contact pads (e.g. 1023, 1022 ofFIG. 1), which keep portions of an actuator in a fixed position relativeto the housing, permitting the actuator to drive a lead screw in arotational mode. For example, the actuator contact pads 1020 prevent theactuator 20 from rotating relative to the housing.

In addition to coupling the actuator 20 to the lead screw, the preloadspring 10 provides a preload to the bearings upon which the lead screwturns. Typically bearings are coupled to the housing and located at thelead screw retention wells 1051 and 1065. In some embodiments,additional bearings are located at the gear lash spring referencefeature 1063. To function properly, many bearing designs require thatsome minimal constraining force be supplied to hold the various portionsof the bearing together. This force is typically termed the ‘preload’.In some embodiments of the present invention, the preload spring exertsforces on the bearings located within the lead screw retention wells1051 and 1065.

The present invention contemplates a variety of means for interfacebetween actuators and lead screws. For example, FIG. 12A illustrates apreferred interface in accordance with the present invention, in thiscase between the actuator 20 and the lead screw 60. The actuator 20 iscoupled with a non-threaded region of the lead screw 60. A feature ofthe actuator 20 is urged against an actuator-registering feature 63 ofthe lead screw 60, by the preload spring 10, which exerts forces againstthe housing 1 and the actuator 20. In this example, theactuator-registering feature 63 is disposed between the non-threadedregion and the threaded region of the lead screw 60, where thenon-threaded region has a smaller outer diameter than the threadedregion, and a second relatively short non-threaded region is disposedbetween the actuator-registering feature 63 and the threaded region.

In another example, FIG. 12B illustrates an interface in accordance withthe present invention, in this case between the actuator 20′ and thelead screw 60′. The actuator 20′ is coupled with a non-threaded regionof the lead screw 60′. A feature of the actuator 20′ is urged against anactuator-registering feature 63′ of the lead screw 60′, by the preloadspring 10, which exerts forces against the housing 1 and the actuator20′. In this example, the actuator-registering feature 63′ is disposedbetween the non-threaded region and the threaded region of the leadscrew 60, where the non-threaded region and the threaded region haveapproximately equal outer diameters.

In another example, FIG. 12C illustrates an interface in accordance withthe present invention, in this case between the actuator 20″ and thelead screw 60″. The actuator 20″ is coupled with a non-threaded regionof the lead screw 60″. A feature of the actuator 20″ is urged against anactuator-registering feature 63″ of the lead screw 60″, by the preloadspring 10, which exerts forces against the housing 1 and the actuator20″. In this example, the actuator-registering feature 63″ is disposedbetween the non-threaded region and the threaded region of the leadscrew 60, where the non-threaded region has a narrower outer diameterthan the threaded region, and a second relatively long non-threadedregion is disposed between the actuator-registering feature 63 and thethreaded region.

In another example, FIG. 12D illustrates an interface in accordance withthe present invention, in this case between the actuator 20′″ and thelead screw 60′″. The actuator 20′″ is coupled with a non-threaded regionof the lead screw 60′″. A feature of the actuator 20′″ is urged againstan actuator-registering feature 63′″ of the lead screw 60′″, by thepreload spring 10′″, which exerts forces against the housing portion 2and the actuator 20′″. In this example, the actuator-registering feature63′″ is disposed between the non-threaded region and the threaded regionof the lead screw 60, and the non-threaded region has a relativelylarger outer diameter than the threaded region. Also, the preload spring10′″ and housing portion 2 are disposed between the non-threaded regionand the threaded region.

Coupling Nut

A lead screw assembly typically includes a coupling nut. Preferably, acoupling nut includes teeth configured to interface with the threadedregion of the lead screw. The teeth of the coupling nut perform severalfunctions, discussed below. In the typical configuration, the teeth areconfigured such that rotation of the lead screw causes translation ofthe coupling nut along the long axis of the lead screw. For example, InFIG. 1, as the lead screw 200 rotates, the coupling nut 230 istranslated along the z-axis of the lead screw. The direction oftranslation is correlated to the direction of rotation, with the precisecorrelation depending on the lead screw thread direction.

A coupling nut is also typically coupled to the housing via at least onespring configured to bias the teeth of the coupling nut relative to thelead screw threads. For example, the lead screw assembly 300′ of FIG. 3includes an anti-gearlash spring 40. The anti-gearlash spring ispreferably separate from the actuator pre-load spring. Referring now toFIG. 5A, the lead screw assembly 200 includes the anti-gearlash spring240 disposed between and exerts spring forces on each of the couplingnut 230 and the gearlash spring reference feature 1063 of the frontcomponent 1060 of the housing. Also, the pre-load spring 210 is disposedbetween and exerts spring forces on each of the actuator 220 and theface of the rear component 1050 adjacent to the lead screw retentionwell 1051.

Further, the anti-gearlash spring is separately coupled to the housingfrom the preload spring, such that the spring forces of the two springsare mechanically isolated from each other. Several features of the leadscrew assembly configuration help isolate the spring forces: 1) therigid coupling of the rear component 1050 and front component 1060 toform the housing, 2) the rigidity of the lead screw 260, 3) the threadedregion 205 of the lead screw 260 constrains axial movement of thecoupling nut 230, and 4) the actuator-registering feature 263 constrainsaxial movement of the actuator 220.

Lens-Coupling Nut Interface

Referring now to FIG. 6, the primary guide sleeves 410 and 510 of thefront optics group 400 and rear optics group 500 (e.g. shown in FIG. 2),respectively, couple with the lead screws through the coupling nuts 230and 330. Both primary guide sleeves 410 and 510 couple with the primaryguide pin 600. The rear primary guide sleeve 510 includes a protrudingfeature 512 that interfaces with a slotted feature of the coupling nut330. A perspective view of the interface between the protruding feature512 and the slotted feature of the coupling nut 330 is illustrated inFIG. 5B. The slotted feature is formed by the arms 335, and includes thereference surfaces 336. The references surfaces 336 protrude into theslotted feature of the coupling nut 330 to form a gap sized to acceptthe protruding feature 512. Preferably, the gap and protruding feature512 are sized to fit together with substantially zero ‘play’ between thetwo parts.

Similarly, the front primary guide sleeve 410 includes a protrudingfeature 412 that interfaces with a slotted feature of the coupling nut230. The slotted feature is formed by the arms 235, and includes thereference surfaces 236. The reference surfaces 236 protrude into theslotted feature of the coupling nut 230 to form a gap sized to acceptthe protruding feature 412. Preferably, the gap and protruding feature412 are sized to fit together with substantially zero ‘play’ between thetwo parts.

In this preferred configuration, movement of a coupling nut along a leadscrew axis results in translation of its counterpart guide sleeve alonga guide pin. Since the guide sleeves are each a rigidly coupledcomponent of an optics group, translation of a coupling nut results intranslation of its counterpart optics group. However, a simple rigidconnection between a coupling nut and a guide sleeve could accomplishthis function. The illustrated configuration provides additionalbenefits by isolating the guide sleeve from non-translational movementsof the coupling nut. The small contact area between the referencesurfaces and the protruding feature of a guide sleeve serves to minimizefriction, permitting movement of the coupling nut relative to the guidesleeve in the axes orthogonal to the axis of the lead screw. Thisconfiguration isolates most mechanical vibration or disturbance of thecoupling nut from the optics group. Further, the isolation means thatonly the translational degree of freedom of the coupling nut need becontrolled to achieve a required precision for positioning of the opticsgroup.

The springs include in a typical lead screw assembly serve multiplepurposes. For example the anti-gearlash spring couples a lead screwreference feature to a coupling nut. This coupling exerts spring forceson each element, biasing the coupling nut away from the referencefeature.

C. Functional

The front optics group 400 is part of a first optics assembly thatincludes the first lead screw assembly 200. The rear optics group 500 ispart of a second optics assembly that includes the second lead screwassembly 300. Together with other elements of the module 1000, the firstand second optics assemblies provide for controlled movement andpositioning of the optics groups 400 and 500 relative to the imagesensor 1010.

The lead screw assembly 200 includes a threaded region 205. The couplingnut 230 provides an interface between the optics group 400 and thethreaded region 205; translating rotation of the lead screw 260 intotranslation of the optics group 400. The coupling nut 230 in combinationwith other elements of the lead screw assembly 200 translates withoutbinding and allows for hard stoppage of the optics group 400 forexternal referencing.

The lead screw assembly 200 also includes the actuator 220, which isconfigured to drive movement of the optics group 400 by rotating thelead screw 260. The configuration of the actuator 220 in combinationwith the various spring elements of the lead screw assembly 200 avoidshigh friction loads on the coupling nut 230 and allows for efficienttransmission of energy from the actuator to the lead screw 260.

The lead screw assembly 300 includes a threaded region 305. The couplingnut 330 provides an interface between the optics group 500 and thethreaded region 305; translating rotation of the lead screw 360 intotranslation of the optics group 500. The coupling nut 330 in combinationwith other elements of the lead screw assembly 300 translates withoutbinding and allows for hard stoppage of the optics group 500 forexternal referencing.

The lead screw assembly 300 also includes the actuator 320, which isconfigured to drive movement of the optics group 500 by rotating thelead screw 360. The configuration of the actuator 320 in combinationwith the various spring elements of the lead screw assembly 300 avoidshigh friction loads on the coupling nut 330 and allows for efficienttransmission of energy from the actuator to the lead screw 360.

The primary guide pin 600 and secondary guide pin 700, in combinationwith the optics groups 400 and 500, and coupling nuts 230 and 330,maintain alignment of the optical elements of the optics groups overtheir range of motion without binding.

The inclusion of position sensing targets 250 and 350 within the leadscrew assemblies 200 and 300, in combination with the position sensors1030 of the module 1000 permits use of non-linear actuators, e.g. 220,320, to drive the lead screws 260, 360.

D. Operational Details

Guide Pin Arrangement

Referring now to FIG. 5B, the front guide sleeve 410 of the front opticsgroup is elongated relative to the length of the front barrel 430 (FIG.5A). Similarly, the rear optics group 500 includes the elongated rearguide sleeve 510, which couples with the primary guide pin 600. Thisconfiguration prevents the optics groups 400 and 500 from rotatingwithin the y-z plane or x-z plane relative to the primary guide pin 600,but permits rotation within the x-y plane, assuming the guide pin 600lies along the z-axis. Further, the guide sleeves are rigidly connectedto the barrels. This configuration prevents the optics groups fromrotating within the y-z plane or x-z plane relative to the primary guidepin 600, but permits rotation within the x-y plane, assuming the guidepin 600 lies along the z-axis.

Referring now to FIG. 1, the front optics group 400 also includes thefront guide slot 420, configured to couple with the secondary guide pin700. Similarly, the rear optics group 500 includes the rear guide slot520. The coupling between the guide slots and the secondary guide pin700 prevents the front and rear optics groups from rotating within thex-y plane relative to either of the guide pins 600 and 700. The couplingbetween the front and rear optics group and guide pins 600 and 700permits the optics groups to translate along the axis defined by the twoguide pins (the z-axis in FIG. 1), but not to move in either of the axesorthogonal to that axis (here the x and y axes).

Screw-Lens Coupling

FIGS. 4, 7A, and 7B illustrate further details of an interface between acoupling nut and a lead screw in accordance with some embodiments of thepresent invention. In some embodiments, as shown in FIG. 4, male threadsof a lead screw 260 interlock with the teeth threads of the coupling nut230. However, in some embodiments, other configurations are used. Forexample, as shown in FIG. 7A, a coupling nut 2230 preferably includes afirst coupling arm 2231 and a second coupling arm 2232, each of whichare urged against the lead screw 2260 by the spring 2233. Further, thecoupling nut 2230 interfaces with a guide sleeve 2510. Preferably, theguide sleeve 2510 and the coupling nut 2230 are ‘soft’ coupled so thatonly movements aligned with the guide screw/guide pin axes aretranslated between the two.

FIG. 7B illustrates the interface between the coupling teeth 2231′ and2232′, of the coupling arms 2231 and 2232 respectively, and the screwthreads 2261 of the lead screw 2260. The coupling teeth 2231′ and 2232′have a flatter thread angle than the screw threads 2261. Stated anotherway, the (radially measured) height of the screw threads 2261 exceedsthe height of the coupling teeth 2231′ and 2232′. This arrangementnecessitates that the teeth and threads have different pitches. Asillustrated, the pitch of the coupling teeth 2231′ and 2232′ preferablyexceeds the thread pitch of the screw threads 2261. The pitch of thescrew threads 2261 is preferably constant along the lead screw 2260.Thus, while the coupling nut 2230 moves along the lead screw 2260 aconstant ratio is maintained between the pitch of the coupling teeth2231 and 2232′ and the threads with which they couple.

The gradient in thread angle between the coupling teeth 2231′ and 2232′and the screw threads 2261, in combination with the urging of thecoupling arms 2231 and 2232 by the spring 2233, permits for referencingof the optics group via a mechanical hard stop of the coupling nut 2230.In male thread-female thread couplings, a mechanical hard stop of thecoupling nut whilst the lead screw is turning can lead to binding andthread damage. In contrast, in the illustrated system, if the lead screw2260 is driven during mechanical hard stop of the coupling nut 2230, thesteep screw threads 2261 act as a wedge against the flat coupling nutteeth 2231′ and 2232′, extending the spring 2233 and driving thecoupling arms 2231 and 2232 apart. Thus, a mechanical hard stop of thecoupling nut 2230 during rotation disengages the coupling teeth 2231′and 2232′ from the thread teeth 2261, preventing binding. This permitsposition referencing of an optics group coupled to the coupling nut viaa hard mechanical stop without precise switching of the lead screwactuator during referencing.

Furthermore, the gradient and the spring force provide a naturalcentering of each coupling tooth between the two thread portions withwhich it interacts. So long as the spring applies force evenly to eachcoupling tooth, the tooth naturally rests in a defined position relativeto the thread portions. This centering reduces the incidence of“backlash” that can occur between a nut and bolt with threads of matchedpitch and angle. Backlash is the jittering of the nut relative to thebolt when there is room for the nut thread to move within the groove ofthe bolt thread.

Referring now to FIG. 3, the anti-gearlash spring 40 also assists inpreventing backlash. The spring 40 produces a spring force urging thecoupling nut 30 away from the gearlash spring reference feature 1063.The teeth of coupling nut 30 are typically engaged with the thread ofthe threaded portion 5 of the lead screw, hence the spring force pushesthe teeth of the coupling nut 30 toward the face of the thread proximalto the gearlash spring reference feature 1063.

Actuator Configuration

Referring now to FIG. 4, some embodiments of the present inventioninclude an actuator 220 configured with a lead screw 260 to permitrotation of the lead screw 260 by the actuator 220. Preferably,embodiments of the present invention include features adapted to ensureefficient operation of the actuators.

For example, some embodiments of the present invention employcylindrical vibrational actuators configurable to drive rotation of anon-threaded shaft. Exemplary actuators of this type are piezoelectricultrasonic motors that interface with a non-threaded shaft throughfriction, causing the shaft to rotate without translating. Preferablythe cylindrical actuators cause rotation of a shaft positionedtherewithin when excited in resonant modes of vibration. These actuatorsare advantageously operated in a defined space with a substantiallyconstant set of forces acting upon them.

FIGS. 4 and 6 illustrate a preferable configuration of actuators 220 and320 in accordance with the present invention. As mentioned above, thevibrational actuators 220 and 320 operate with greater efficiency whenthey coupled in a defined space by substantially constant-force means.For example, as illustrated in FIG. 4, the preload spring 210 urges theactuator 220 against the actuator-registering feature 263 of the leadscrew. This coupling forms a normal force between the actuator 220 andthe actuator-registering feature 263, which increases any potentialfrictional force between the actuator 220 and the lead screw 260.Because the actuator 220 drives rotation of the lead screw 260 viafriction, the preload spring 210 increases the potential drive force ofthe actuator 220. However, overly high frictional forces between theactuator 220 and the lead screw 260 can decrease the attainable rate oflead screw rotation. Preferably, the strength of the preload spring 210is chosen to optimize efficiency while permitting a sufficiently highrate of rotation.

Further, in the illustrated embodiment, the normal force between theactuator registering feature 263 and the actuator 220 is solelydetermined by the preload spring 210. Though the anti-gearlash spring205 exerts forces elsewhere along the lead screw assembly 200, theseforces are isolated from the actuator 200. The actuator 200 does nottranslate along the lead screw 260, so the spacing between the actuator220 and the housing 1050 remains constant. Thus, because the forceexerted by the preload spring 210 upon both the actuator 220 and thehousing 1050 is proportional to the spacing therebetween, the forceremains substantially constant during operation of the actuator 220.

As shown in FIG. 6, the preload spring 310 provides analogous functionsfor the actuator 320 within the lead screw assembly 300. In addition,FIG. 6 illustrates the coupling of selected points on the actuator 320via the actuator contact pads 1023 to the housing 1050.

As mentioned, the actuator 320 benefits from operating in a definedspace. The preload spring 310 serves to maintain the actuator 320 withina longitudinal region of the lead screw 360. However, the preferred typeof actuator employed within the illustrated embodiment requiresadditional stabilization to exert a rotational force on a lead screw.Interaction between the actuator and a lead screw causes rotation of onerelative to the other. Because the module 1000 requires the lead screw360 to rotate relative to the housing 1050, the actuator 320 isrotationally secured to the housing 1050 by the actuator contact pads1023.

Aspects of the positioning and construction of the contact pads 1023 areadapted to minimize any negative effect on the efficiency of theactuator 320. The actuator contact pads 1023 are located at positions,called node points, on the actuator 320 that are substantiallystationary during operation of the actuator 320 at a preferred set ofresonances. In addition, the contact pads 1023 are preferablyconstructed of a resilient material configured to stretch and rebound,permitting limited movement of the node points away from their restpositions.

Though two actuator contact pads 1023 are illustrated in FIG. 6, someembodiments have a greater number, while other embodiments have fewer.In addition, the actuator contact pads 1022 perform a similar functionin coupling the actuator 220 to the housing 1050 to permit rotation ofthe lead screw 260.

Preferably, embodiments of the present invention employ feedback from aposition sensing system to control the actuators. Employing such afeedback system permits use of non-linear actuators within embodimentsof the present invention and facilitates repeatability.

Referencing

Advantageously, some embodiments of the present invention includefeatures adapted to permit hard mechanical stop of the lens groupswithout mechanical binding of the system. Such mechanical stoppage ispreferably used for referencing in controlling positioning of the lensgroups.

Referring now to FIGS. 7A and 7B, the gradient in thread angle betweenthe coupling teeth 2231′ and 2232′ and the screw threads 2261, incombination with the urging of the coupling arms 2231 and 2232 by thespring 2233, permits for referencing of the optics group via amechanical hard stop of the coupling nut 2230. In male thread-femalethread couplings, a mechanical hard stop of the coupling nut while thelead screw is turning can lead to binding and thread damage. Incontrast, in the illustrated system, if the lead screw 2260 is drivenduring mechanical hard stop of the coupling nut 2230, the steep screwthreads 2261 act as a wedge against the flat coupling nut teeth 2231′and 2232′, extending the spring 2233 and driving the coupling arms 2231and 2232 apart. Thus, a mechanical hard stop of the coupling nut 2230during rotation disengages the coupling teeth 2231′ and 2232′ from thethread teeth 2261, preventing binding. This permits position referencingof an optics group coupled to the coupling nut via a hard mechanicalstop without precise switching of the lead screw actuator duringreferencing.

Position Sensing

As mentioned elsewhere, some embodiments of the present inventioninclude position-sensing features configured to provide feedback to anactuator control system to permit accurate positioning despite use ofnon-linear actuator motors. An exemplary position sensing systemcomprises the position sensors 1030 and the position sensing targets 250and 350 of the module 1000 of FIG. 1.

A position sensing system provides position data for a lens group overits range of motion. In some embodiments of the present invention, aposition sensing system tracks the relative position of an optics groupto within 10 microns over a range of 10 mm.

In some embodiments, a reflection encoding sensor coupled with acylindrical sensing target are used to measure rotations of a leadscrew. Since the optics group is coupled with the lead screw, which hasknown thread pitch, lead screw rotation is proportional to translationof the optics group along the lead screw axis.

A more detailed view of a position sensing system employed within someembodiments of the present invention is shown in FIG. 10. Theemitter/detector 3030 comprises the first sensor 3034A, the secondsensor 3034B, and the emitter 3032. The mask structure 3030′ includesthe emitter window 3032′ and the four sensor windows 3034A′, 3034A″,3034B′, and 3034B″. In some embodiments the emitter/detector 3030 is aphotoreflector. In some embodiments the emitter is an LED.

The dark bands of the sensing target 3350 absorb radiation emitted fromthe emitter, while the light bands of the sensing target reflectradiation emitted from the emitter. The sensors detect transitions inabsorption and reflectance as the bands move relative to the sensorwindows. Both the first sensor 3034A and the second sensor 3034B detecttransitions. Preferably, the second sensor 3034B detects transitions outof phase with the first detector 3034A. Thus, by combining theout-of-phase data from the two sensors, a control system can detect thedirection of movement as well as its magnitude. Though the sensingsystem is illustrated with a cylindrical scanning target, someembodiments of the present invention include similar systems usinglinear targets.

In traditional reflection encoding, the radiation used cannot be overlydiffused by the time it reaches the sensing target. FIG. 8B illustratesthe optimal maximum beam spreads for a series of light sources (whitesquares on left hand side) emitting light towards a series of absorptiveand reflective bands (right hand side). The detail shown in FIG. 8Cillustrates a 20-micron wide light source. In this case, the maximumoptimal spread is 10 microns. Under normal conditions, this means thegap ‘d’ should be less than 56.7 microns. Thus, for the relativelynarrow features shown in the apparatus of FIG. 10, the tolerancerequired would be quite small.

However, embodiments of the present invention include a variety offeatures and configurations adapted to loosen these tolerances ordecrease problems caused by diffusion of the radiation used duringreflection encoding.

Some techniques involve hardware or software measures that permit theuse of lower resolution targets. Some embodiments employ additionalhardware and/or firmware (e.g. a clock for timing and for analysis) toperform linear interpolation between detected transitions. However, ifthe actuator is very non-linear, interpolation can introduce positioningerror.

Some embodiments employ a lower resolution target with a repeatedpattern, but use additional processing of the sensor data to providehigher effective resolution. Examples include the detection of multiplethresholds during a transition recorded within sensor data via analogcircuitry and converting the output to digital. However, suchembodiments require the inclusion of analog circuitry and additionalcalibration of an analog/digital converter during sensing. In some ofthese embodiments, calibration is accomplished automatically duringpower on.

Some embodiments employ a combination of linear interpolation andanalog-digital converter circuitry to permit use of lower resolutiontargets. By employing these and other techniques, embodiments of thepresent invention can use lower resolution targets.

Preferably, the use of lower resolution sensing targets permitsconfigurations in which only a small number of features of the targetare within the field of view of a sensor at any given moment. A systemof this type is illustrated in FIG. 8A. As shown by the cross sectionalview, a position sensing system includes the cylindrical target 3350positioned a distance d from the emitter/detector 3030. The field ofview of the emitter/detector 3030 subtends a region of the target 3350that includes a maximum of two transitions. In some embodiments theemitter/detector is a photoreflector. Preferably, a single feature (e.g.a stripe) dominates the field of view. Thus, the potential for artifactsor errors in transition detection is minimized. Typically, the featuresize of the target is chosen based on the field of view. However, therequired resolution can also be a factor in determining feature size.

FIG. 11 is a more detailed view of a position sensing system employedwithin some embodiments, including the preferred embodiment, of theinvention. The emitter/detector 4030 comprises the sensor 4034, theemitter 4032. The mask structure 4030′ includes the emitter window 4032′and the two sensor windows 4034′ and 4034″. In some embodiments theemitter is an LED.

The dark bands of the sensing target 4350 absorb radiation emitted fromthe emitter, while the light bands of the sensing target reflectradiation emitted from the emitter. The sensors detect transitions inabsorption and reflectance as the bands move relative to the sensorwindows. Preferably, the sensor 4034 separately detects transitions inboth sensor windows 4032′ and 4034″. In some embodiments theemitter/detector 4030 is a photoreflector.

In some embodiments, the sensor 4034 is capable of detecting transitionsout of phase between the two windows. In these embodiments, by combiningthe out-of-phase data from the two sensors, a control system can detectthe direction of movement as well as its magnitude. Though the sensingsystem is illustrated with a cylindrical scanning target, someembodiments of the present invention include similar systems usinglinear targets.

In some embodiments, each feature covers 60 degrees of the circumferenceof the cylindrical target. Thus, in one embodiment, a cylindrical targethaving a 12 mm circumference includes six 2 mm stripes in an alternatingreflective/absorptive pattern. However, if a resolution greater than sixcounts per revolution of the sensing target is required, additionalprocessing steps as outlined above are preferably employed.

In addition, some embodiments perform additional processing steps on theradiation emitted from the LED before providing it to the sensingtarget. The method shown in FIG. 10 is termed direct imaging. Anotherexample of direct imaging is illustrated in FIG. 9A. Radiation from anemitter (white rectangle) reflects from a target to a detector (hatchedrectangle). Direct imaging requires the target and the sensor to be verynear to one another.

FIG. 9B illustrates a system in which a lens is used to collimateradiation from a detector. Collimation permits the target-sensordistance to increase. The maximum distance and tolerances are determinedby the spreading of the radiation.

FIG. 9C illustrates a system in which a pinhole is used to prevent‘bleed over’ from an adjacent region from preventing detection of atransition. In this case, reflected radiation must pass through thecentered pinhole placed near to the target surface before reaching thedetector. This system can require higher intensity LEDs, as relativelylittle light is available through the pinhole.

E. Advantages

As illustrated in the foregoing examples, the module of some embodimentsis set to a continuum of different optical positions byelectromechanical controls. These different optical positionsadvantageously provide a variety of picture taking modes. Via repeatablepositioning and software control, the various positions and/orpicture-taking modes can be optimally pre-set to fixed focusconfigurations for the module. Hence, some of the embodiments describedabove provide a variety of fixed focal lengths in a small form factor.These embodiments advantageously allow more sophisticatedimplementations for small devices that typically have limited capacityfor multi focal optical and/or camera mechanisms. For instance, someembodiments advantageously include a plurality of focal and zoompositions in otherwise simple and compact devices. Since the describedembodiments require limited range of motion, and have minimal spacerequirements, these embodiments have a variety of applications in ultracompact portable devices, such as, for example, in mobile phones andother consumer electronics. Some particular medical device applicationsinclude

Further, while realizing the benefits of multi focal functionality, theembodiments described above require little space and require only alimited range of motion, while having a low cost.

As described above, the optical elements of some embodiments are dividedinto two groups, one group housed in a front barrel, the other grouphoused in a rear barrel. For example, as shown in FIG. 4, the frontgroup comprises the lenses 440, 442, 444, and 446, while the rear groupcomprises the lenses 540, 542, 544, and 546. Typically, the precisemotion of these optics groups group within confined spaces is achievedby using the mechanism(s) described above.

The form factor of the auto-focus and zoom module of some embodiments isapproximately 10×14×22 mm without a prism or approximately 10×14×30 mmincluding a prism.

While the invention has been described with reference to numerousspecific details, one of ordinary skill in the art will recognize thatthe invention can be embodied in other specific forms without departingfrom the spirit of the invention. Thus, one of ordinary skill in the artwill understand that the invention is not to be limited by the foregoingillustrative details, but rather is to be defined by the appendedclaims.

1. A method of preventing backlash in a system using a threaded leadscrew as a drive element, comprising the steps: a. providing a leadscrew having an axis and a threaded region with a thread depth andthread pitch; and b. providing a spring-hinged assembly of a pluralityof teethed coupling arms arranged in opposition and configured to couplewith the threaded portion of the lead screw, wherein teeth of theteethed coupling arms have a tooth depth and tooth pitch, wherein thetooth depth is substantially less than the thread depth, and the toothpitch is greater than the thread pitch, such that the gradient in thethread angle between the coupling teeth and the screw threads incombination with the urging of the coupling arms by the spring hingeprovide a natural centering of each coupling tooth between the twothread portions with which it interacts.
 2. The method of preventingbacklash in a system using a threaded lead screw as a drive element asin claim 1, wherein driving the lead screw during a mechanical hard stopof the spring-hinged assembly of the plurality of teethed coupling arms,causes the screw threads to act as a wedge against the coupling teeth,extending the spring and driving the teethed coupling arms apart,disengaging the coupling teeth from the thread teeth.
 3. The method ofpreventing backlash in system using a threaded lead screw as a driveelement as in claim 2, wherein the mechanical hard stop is used as aposition reference.
 4. The method of preventing backlash in a systemusing a threaded lead screw as a drive element as in claim 1, whereinthe lead screw is driven by an actuator via friction and a preloadspring increases the potential drive force of the actuator.
 5. Themethod of preventing backlash in a system using a threaded lead screw asa drive element as in claim 4 wherein the strength of the preload springis selected to optimize efficiency in speed of rotation.
 6. The methodof preventing backlash in a system using a threaded lead screw as adrive element as in claim 4 wherein the strength of the preload springis selected to optimize efficiency in drive force applied by theactuator to the lead screw.
 7. A translation assembly with backlashprevention comprising: a. a threaded lead screw as a drive element, thelead screw having an axis and a threaded region with a thread depth andthread pitch; and b. a spring-hinged assembly of a plurality of teethedcoupling arms arranged in opposition and configured to couple with thethreaded portion of the lead screw, wherein teeth of the teethedcoupling arms have a tooth depth and tooth pitch, wherein the toothdepth is substantially less than the thread depth, and the tooth pitchis greater than the thread pitch, such that the gradient in the threadangle between the coupling teeth and the screw threads in combinationwith the urging of the coupling arms by the spring hinge provide anatural centering of each coupling tooth between the two thread portionswith which it interacts.
 8. The translation assembly with backlashprevention as in claim 7, wherein driving the lead screw during amechanical hard stop of the spring-hinged assembly of the plurality ofteethed coupling arms, causes the screw threads to act as a wedgeagainst the coupling teeth, extending the spring and driving the teethedcoupling arms apart, disengaging the coupling teeth from the threadteeth.
 9. The translation assembly with backlash prevention as in claim8, wherein the mechanical hard stop is used as a position reference. 10.The translation assembly with backlash prevention as in claim 7, whereinthe lead screw is driven by an actuator via friction and a preloadspring increases the potential drive force of the actuator.
 11. Thetranslation assembly with backlash prevention as in claim 10 wherein thestrength of the preload spring is selected to optimize efficiency inspeed of rotation.
 12. The translation assembly with backlash preventionas in claim 10 wherein the strength of the preload spring is selected tooptimize efficiency in drive force applied by the actuator to the leadscrew.
 13. The translation assembly with backlash prevention as in claim7, further comprising: a. an image sensor; b. an optics group coupled toa threaded portion of the lead screw in the translation assembly;wherein the rotation of the lead screw in the translation assemblyresults in translation of the optics group along an axis of the leadscrew in the translation assembly; wherein the optics group isconfigured to provide an image having a focus and a magnification to theimage sensor.
 14. The first and a second translation assembly withbacklash prevention as in claim 7, further comprising: a. an imagesensor; b. a first optics group coupled to a threaded portion of thelead screw in the first translation assembly; wherein rotation of thelead screw in the first translation assembly results in translation ofthe first optics group along an axis of the lead screw in the firsttranslation assembly; c. a second optics group coupled to a threadedportion of the lead screw in the second translation assembly; whereinrotation of the lead screw in the second translation assembly results intranslation of the second optics group along an axis of the lead screwin the second translation assembly; and wherein the first optics groupand the second optics group are configured to provide an image having afocus and a magnification to the image sensor.
 15. The personalelectronic device comprising the translation assembly with backlashprevention as in claim 13 wherein the electronic device type is selectedfrom the group of: a. a cellular phone; b. a personal digital assistant;c. a digital camera; d. a wrist watch; e. a pocket watch; f. a videocamcorder.
 16. The personal electronic device comprising the first andsecond translation assemblies as in claim 14 wherein the electronicdevice type is selected from the group of a. a cellular phone; b. apersonal digital assistant; c. a digital camera; d. a wrist watch; e. apocket watch; f. a video camcorder.